1. Field of the Invention
The present invention relates to a liquid discharge head, having plural nozzle apertures, plural pressure generating chambers respectively communicating with the nozzle apertures, and a reservoir communicating with the plural pressure generating chambers, wherein a liquid droplet is discharged from each of the plural nozzle apertures by a discharge energy generated in each of the pressure generating chambers.
2. Related Background Art
A liquid discharge head, which applies a pressure to liquid thereby generating a flying liquid droplet, is widely utilized as a relatively inexpensive output device of a high performance. It is particularly utilized as photograph output means in combination with the recent pervasiveness of digital cameras, and the requirement for image quality is becoming stricter year after year. For this purpose, a finer discharged liquid droplet and a denser structure of liquid flow paths are essential requirements, and a producing method for the liquid discharge head has been proposed, utilizing a micromachining technology, which precisely prepares fine patterns on a silicon substrate, relatively simply by an anisotropic etching and the like.
For example Japanese Patent Application Laid-Open No. H07-156399 discloses, as shown in FIG. 5, an ink jet head prepared by integrally forming flow paths such as pressure generating chambers 503 and a reservoir, and vibrating plates 504 by applying an anisotropic etching on a silicon substrate, and adjoining a nozzle plate 501 having nozzle apertures 502. Such ink jet head, utilizing dependence of etching rate on the plane orientation of silicon single crystal, can prepare flow paths in precise and simple manner, and, involving the adjoining operation only in the nozzle plate 501, enables a simple manufacturing process with little intrusion of adhesive material into the flow paths and with a high reliability.
Also Japanese Patent Application Laid-Open No. H05-229128 discloses a producing method for an ink jet head which is prepared, as shown in FIG. 6, by applying an anisotropic etching to a silicon substrate to obtain a flow path substrate 600 integrally bearing pressure generating chambers 602 and nozzle apertures 601, to which a vibrating plate 605 having piezoelectric elements 606 is adjoined.
However, the invention disclosed in Japanese Patent Application Laid-Open No. H07-156399 involves following drawbacks:
(1) As the dependence of etching rate on the plane orientation of silicon single crystal is utilized, the usable substrate is limited and inevitably involves an increased cost;
(2) As the depth of the pressure generating chamber is determined by the thickness of the substrate, the depth of the pressure generating chamber and the thickness of the substrate cannot be determined independently. In case of arranging the pressure generating chambers at a high density, an increased depth of the pressure generating chamber renders a partition wall, between the adjacent pressure generating chambers, easily flexible, thus resulting in problems such as a pressure loss and a crosstalk. On the other hand, a large-area substrate is advantageous in cost in mass production, but a thin substrate involves a problem in handling, thus resulting in a trade-off relationship with the depth of the pressure generating chamber mentioned above;
(3) As the ink jet head is prepared by adjoining the flow path substrate bearing flow paths and the nozzle plate, the alignment between the flow path substrate and the nozzle plate becomes more difficult as the density of the structures increases. Thus, the reliability becomes lower particularly in a color-recording multi nozzle head requiring a large number of nozzles. Also in case the material of the nozzle plate and the silicon constituting the flow path substrate have different thermal expansion coefficients, the nozzle plate may become easily peelable by a temperature change involved in the manufacturing process or in the environment of use, thus deteriorating the reliability.
On the other hand, in the method disclosed in Japanese Patent Application Laid-Open No. H05-229128, since the flow paths including the pressure generation chambers and the nozzle apertures are formed in a same substrate, the aforementioned drawback relating to the adjoining of the nozzle plate and the flow path substrate no longer exists. However, as the flow paths are formed by anisotropic etching, the limitations on the usable substrate and on the producible shape remain the same. Also the thickness of the substrate is equal to a sum of the depth of the pressure generating chamber and the length of the nozzle aperture, so that the pressure generating chamber has to be made deeper or the nozzle aperture has to be made longer in order to use a thick substrate that is convenient for handling. However, a deeper pressure generating chamber leads to the aforementioned drawbacks of pressure loss or crosstalk, and a longer nozzle leads to an increased flow path resistance.